4+/ NRELISR-520-2475 9 M. Stern, G. Duran, G. Fourer, K. Mackamul, W. Whalen, M. Van Loo, and R. West Utility Power Group Chatsworth, California NREL technical monitor: H. Thomas National Renewable Energy Laboratory 16 17 Cole Boulevard Golden, Colorado 80401-3393 A national laboratory of the U. S. Department of Energy Managed by Midwest Research Institute for the U. S . Department of Energy under Contract No. DE-AC36-83CH10093 Prepared under Subcontract No. ZAF-5-1427 1-06 June 1998 2 DISCLAIMER This report was prepared as an account of work sponsored by an agency of the United States Government. Neither the United States Government nor any agency thereof, nor any of their employees, make any warranty, express or implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, apparatus, product, or process disclosed, or represents that its use would not infringe privately owned rights. Reference herein to any specific commercial product, process, or service by trade name, trademark, manufacturer, or otherwise does not necessarily constitute or imply its endorsement, recommendation, or favoring by the United States Government or any agency thereof. The views and opinions of authors expressed herein do not necessarily state or reflect those of the United States Government or any agency thereof. DISCLAIMER Portions of this document may be illegibie electronic image products. images are produced from the best available original document. LIST OF FIGURES Figure 1. UPG’s PVMaT Phase 4Al Integrated Solar Tracking Sub-Array. 6 Figure 2. Photograph of I00 kW PV power system in Fort Davis, Texas. 9 Figure 3. BOS cost group breakdown 10 Figure 4. Phase I Tasks 12 Figure 5. Phase II Tasks 13 Figure 6. Modular Panel design criteria 14 Figure 7: SSI M55 PV Module. 15 Figure 8. SSI SP75 PV Module 16 Figure 9. I1 M55 Modular Panel. 18 Figure 10. 7SP75 Modular Panel. 19 Figure II. Modular Panel Manufacturing System. 20 Figure 12. Modular Panel shipping block 21 Figure 13. IPPU Assembly Functions. 25 Figure 14- General IPPU Specifications. 26 Figure 15. IPPU Enclosure. 29 Figure 16. Prototype sub-arrays in Sacramento, California. 31 Figure 17: DC Assembly Factory Test Procedure. 33 Figure 18. IPPU Efficiency and THD results of SNL testing. 34 Figure 19. Photograph of production version IPPU. 35 Figure 20. Final system cost reduction results. 36 Figure 21. PV power system field installation tasks. 37 3 Throughout this report, the following definitions shall apply to the words listed below: Laminate: A glass/EVA/cells/EVA/redlar encapsulated assembly of discrete PV solar cells with tinned copper terminal ribbons penetrating the Tedlar back sheet. A weather tight enclosure attached to the back of a laminate to provide a junction point between a laminate’s terminal ribbons and the PV system’s interconnection wiring. Frame: A structural element attached to the perimeter of a laminate to provide edge protection and facilitate handling and mounting. PV module: A laminate which may or may not be provided with a J-box(es) or frame and is utilized by Utility Power Group in the manufacture of Modular Panels. Inverter: A packaged electronidelectrical assembly which converts DC electricity into AC electricity. Often referred to as a PCU or PCS kower sonditioning unit or system) when coupled with DC and AC interface and disconnect components. IPPU: An integrated Eower processing unit which performs all PCU functions as well as single axis solar tracking motor control. Also may be known as SlPP (system integrated power processor) or CPPU kentral power processing unit) Modular Panel : An electrical and structural assembly of PV Modules. Rail: A galvanized steel structural element of a Modular Panel to which PV modules are attached. All laminates, J-boxes, frames, and PV modules described in this report were manufactured and supplied by Siemens Solar Industries, Inc. from their facility in Camarillo, California. 4 EXECUTIVE SUMMARY This report chronicles Utility Power Group’s (“UPG”) successful two-year Photovoltaic Manufacturing Technology (PVMaT) Phase 4A1 work effort which began in July, 1995. During this period, UPG completed design, fabrication, testing and demonstration of a modular and fully integrated 15-kW-ac, solar tracking PV power system sub-array. The two key and innovative components which were developed are a Modular Panel which optimizes factory assembly of PV modules into a large area, field-deployable, structurally-integrated PV panel, and an Integrated Power Processing Unit which combines all dc and ac power collection, conversion and control functions within a single, field-deployable structurally-integrated electrical enclosure. These two key sub-array elements, when combined with a number of other electrical, mechanical, and structural components, create a low-cost and high- performance PV power system. This system, or sub-array, can be deployed in individual units, or paralleled with any number of other sub-arrays, to construct multi- megawatt PV fields. UPG exceeded its goal of providing a 40% reduction in area-related balance-of- system costs and a 50% reduction in power-related balance-of-system costs by achieving cost reductions of 53% and 52% respectively. The net reduction in the total cost of single-axis solar tracking grid connected PV power systems achieved by UPG was 23.3%. In 1996 and 1997, UPG installed a total of 50 integrated and modular sub-arrays in the United States representing over 700 kW of new PV power systems. When applied to these new systems, UPG achieved a cost reduction resulting in over $1.4 million in savings to UPG’s electric utility customers. These customers include the Sacramento Municipal Utility District, Arizona Public Service, and Detroit Edison. 5 INTRODUCTION The overall goal of this PVMaT Phase 4A1 work effort by Utility Power Group ("UPG") was to substantially reduce the total installed cost of utility-scale grid- connected photovoltaic ("PV") power systems. PV power systems generate electricity via the direct conversion of sunlight into electrical energy and can serve as an environmentally benign and domestically secure source of electricity for utility grid connected peak or intermediate load applications. Considering that almost 700,000 megawatts (MW) of electricity generating capacity exists in the United States alone, PV power systems have only negligibly penetrated the electricity generation market. The dominant factor limiting the use of PV power systems in grid-connected applications today is the capital cost of the total installed system with respect to the annual kilowatt-hours of energy generated. The two primary PV power system capital cost groups are I)PV Modules and 2) Everything Else, which is more commonly referred to by the acronym "BOS" (Balance-Of-System). Historically, 60% of the capital cost of typical grid-connected PV systems were allocated to the PV modules while 40% of the costs were allocated to BOS. Technological improvements are the fundamental drivers to cost reduction in both groups, but the cost groups are also greatly affected by production and installation volume which permits standardization, automation, and integration. The focus of UPG's work effort was on BOS component manufacturing technology, which essentially involved all PV power system engineering, manufacturing, assembly and construction tasks from the receipt of a PV module to the delivery of grid-connected electricity. Working with Siemens Solar Industries (Camarillo, California) to optimize the design of PV modules for power systems applications, UPG's goal was to obtain and demonstrate significant cost reductions in the installed cost of PV power systems. Single-axis solar tracking, which provides over 20% more energy in a typical year than a fixed-axis PV system, was selected as the optimum array configuration upon which the overall design was based. As a leading provider of PV system engineering and construction services, UPG was able to quickly transfer any such cost reductions into the PV power system marketplace. As a result of the success of this Phase 4A1 PVMaT contract, UPG received orders from electric utility customers to manufacture and install over 50 integrated, single-axis solar tracking sub-arrays. They are scheduled for completion in 1997 and 1998. The novel systems-design approach utilized by UPG will be described in the following sections, but can be summarized by the word "integration". Full system integration is the key to obtaining the lowest cost and highest performance PV power systems. 7 BACKGROUND Utility Power Group was formed in 1985 by a team of dedicated and experienced engineers and scientists to commercialize photovoltaic (PV) electricity generation technologies in grid and non-grid connected electric utility applications. From 1985 to 1992, UPG’s primary focus was on developing advanced thin film PV module manufacturing technology. From 1992 onward, the company’s focus shifted to providing PV power system design, engineering, construction, installation, operation and maintenance services to electric utilities, as well as to Government and commercial organizations. In 1993, UPG provided the Sacramento Municipal Utility District with a “turn-key” 200-kW PV power system at the Hedge Substation in Sacramento, California . In 1994, UPG installed a 100-kW PV system in Fort Davis, Texas for Central and South West Services’ Solar Park which required a total of fifty-one separate electrical enclosures to provide dc combining, conduivwire routing, tracker control, disconnect, and inverter functions. Over 2,200 PV modules were individually field installed on the array structures. A single inverter provided dc to ac power conversion, and a single tracker, motor controller, provided solar tracking commands. Upon completion of this project, UPG personnel analyzed the costs associated with the construction of grid-connected PV power systems to determine the potential for, and identify the barriers to, future cost savings. To summarize these analyses, it was determined that a shift in philosophy from “constructing” PV power systems to “manufacturing” PV power systems would have the greatest impact upon BOS cost reduction.